When I was maybe 9 yo (now I'm 17), I began to collect "World of knowledge" magazine (I'm not sure whether it's original title, in Poland was edition with such a title), and at first no. very interesting for me was an article about volcanos. One picture showed clay shape of child who died in Pompei. Description above photo was saying, that Pompei was destroyed by volcano in 79 AD. As I saw the date, I thought it means '79, and I started to imagine about cars and shops covered by volcanic dust :)
A childhood belief about history

others believed things like this
- I thought a tidal wave was acutualy a title wave because if the wave was big enough it had its own title!— Nate
- Even though the title is 'How Bizarre', I always thought he sang "help is on"...Anon
- I thought the song "Party Time" by Moby was actually saying "heart attack" (this was before I knew the title)— Elviessa
- I used to think that the title of Barry Manilow's song "Looks Like We Made It" was "Looks Like Tomatoes".— close2nd
- I thought the song "Karma Police" was actually saying "call the police" before I learned the title— Alberto Richardson
- I used to believe that clay pigeons were pigeon-shaped clay figures.Anon